Sensors for transmitting signals representative of the speed and/or position of a vehicle axle have been known for some time. Sensors of this type are shown in, for example, U.S. Pat. No. 4,189,637 to Hiroshi Takamatsu dated Feb. 19, 1980, and U.S. Pat. No. 3,915,266 to Charles H. Lantz dated Oct. 28, 1975. In each of these patents, the spindle upon which the wheel is mounted is fixed. Therefore, it is possible to run electrical conduits between the sensor and a control unit without any danger of wear, damage, or the like caused by exposure of the conductors to rotatable members. In embodiments where the spindle rotates, the teachings of the patents set forth above would not permit the mounting of the sensor adjacent and end of the spindle, the most desirable location for reasons of serviceability and assembly.
U.S. Pat. No. 4,161,120 to Jean-Claude Cloarec dated July 17, 1979, and U.S. Pat. No. 4,288,746 to Gunther Singbartl dated Sept. 8, 1981 disclose a fixed wheel spindle, a hub rotatably mounted on the spindle, and a proximity type sensor having a rotor mounted on the rotating member and a stator affixed to an adjacent stationary member. Conversely, U.S. Pat. No. 3,652,886 to Hugh E. Riordan et al. discloses a rotatable spindle with the rotor mounted on the rotating member and the stator affixed to an adjacent stationary member. It is to be recognized that these arrangements locate the sensor at positions other than at the accessible end of the spindle, and therefor, are difficult to service, assemble, or disassemble the sensor from the vehicle.
It is often necessary to utilize a sensor which is capable of generating more than one output signal so that more than one parameter may be monitored. For example, in automatic guided vehicles, it is necessary to know both the speed of rotation of the wheel and the position of rotation of the wheel relative to a set point so that the exact position of the vehicle within the facilities in which it operates can be known to a relatively precise degree. An example of a device which is sensitive enough and capable of providing more than one output is known as a resolver. In order to utilize the resolver, a mechanical connection between the input shaft of the resolver and the rotating member is required. Due to the accuracy requirements, it is necessary to connect the resolver in a manner so that only a controlled amount of relative motion between the rotating member and the resolver shaft is permitted. Also, it is necessary to provide a connection which places substantially no side or radial force on the shaft and thereby prevent often encountered premature mechanical failure of the resolver.
The present invention is directed to overcoming one or more of the problems as set forth above.